
function Bomb(){
    
    this.start=function (){
        this.id=setTimeout(function() {
        console.log("boom!!");
    },3000)}
    this.clear=function () {
        clearTimeout(this.id);
    }
}

var b1=new Bomb();
var b2=new Bomb();

b1.start();
b2.start();
b2.clear();